A magnetic resonance imaging apparatus is an apparatus configured to excite a nuclear spin of a test object put in a static magnetic field by an RF (radio frequency) signal of a Larmor frequency, and to reconstruct a magnetic resonance signal generated by the test object as the test object is excited so as to produce an image.
A magnetic resonance imaging apparatus has a gantry and a bed. A cylindrical imaging space is formed in the gantry, and an image of a patient is captured in the imaging space. The bed is arranged next to the gantry, and the patient lies on a top plate provided in an upper portion of the bed before the image is captured. At this time, the top plate has descended to a lower position so that the patient can easily lie. The top plate is movable in a vertical direction, and the vertical shift is performed by a driving mechanism of the bed. In time of imaging, the top plate ascends and then horizontally shifts so as to carry the patient into the imaging space in the gantry. The horizontal shift is performed by the driving mechanism of the bed, as well.
One or a plurality of receiving coils is used for imaging of the patient. The magnetic resonance imaging apparatus has, in lots of recent cases, a connector provided on an end of a cable extended from the receiving coil and a fixed connector provided to the top plate coupled with each other in a removable manner. The bed used in this type of magnetic resonance imaging apparatus includes a plurality of cables laid inside. A signal received by the receiving coil is led, from the fixed connector of the top plate and via the cable inside the bed, to a receiver system provided out of the bed.
For a patient having difficulties in autonomous walking, meanwhile, a stretcher apparatus provided separately from the magnetic resonance imaging apparatus is used as disclosed in Japanese Unexamined Patent Publication No. 2008-12290, etc. The stretcher apparatus is provided with a top plate as well, and the patient is carried into a test room where the magnetic resonance imaging apparatus is installed while lying on the top plate. Then, while the patient is lying on the top plate of the stretcher apparatus, shift the stretcher apparatus to a position where the top plates of the stretcher apparatus and the bed overlap each other. At this time, the top plate of the bed has descended to a low position, and the top plates of the bed and the stretcher apparatus are a certain separation apart. Then, the top plate of the bed ascends and comes into contact with the top plate of the stretcher apparatus. Further, the top plate of the bed ascends as scooping the top plate of the stretcher apparatus up in condition that the top plate of the stretcher apparatus is put on top of the top plate of the bed, and stops at a certain position. Then, the top plate of the bed horizontally shifts, and the top plate of the stretcher apparatus and the patient lying thereon are carried into the imaging space in the gantry together with the top plate of the bed.
The receiving coil is coupled, as described above, with the top plate of the bed (called the bed top plate, hereafter) via the connectors. In the case in which the stretcher apparatus is used, then, the top plate of the stretcher apparatus (called the stretcher top plate, hereafter) comes into contact with the bed top plate when the bed top plate ascends by means of the driving mechanism of the bed, and the top plates are separate from each other when the bed top plate descends.
Thus, if the bed top plate is raised by accident while a receiving coil for the spine remains put on the bed top plate, e.g., the receiving coil and its connection cable may possibly be caught between the bed top plate and the stretcher top plate resulting in being damaged. Further, if a receiving coil for the head or a receiving coil for the abdomen or the chest is fixed to a patient lying on the stretcher top plate and the bed top plate is lowered while such a receiving coil remains coupled with the connector of the bed top plate, the cable of the receiving coil may be possibly pulled downwards as the bed top plate descends resulting in that the receiving coil and the cable are damaged.
Meanwhile, according to an operation ordinarily performed, temporarily stop the ascending operation of the bed top plate shortly before the bed top plate ascends and comes into contact with the stretcher top plate, make sure for safety whether neither an arm nor clothes of the patient are caught between the bed top plate and the stretcher top plate, and then raise the bed top plate again. The above operation assumes a use of the stretcher apparatus. If no stretcher apparatus is used, the temporary stop is unnecessary and is a waste of time.
Thus, a magnetic resonance imaging apparatus which can solve the above problems and a method for controlling such an apparatus are demanded.